<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        *{
            margin: 0;
            padding: 0;
        }
        html,body,.app{
            height: 100%;
        }
        .child{
            height: 100%;
            /* height: 100vh; */
            background-image: linear-gradient(180deg,#2af598 0%,#009efd 100%);
        }
    </style>
</head>
<body>
    <div class="app">
        <div class="child"></div>
    </div>
</body>
</html>